chemarr – Ar­rows for chemists

Very of­ten chemists need a longer ver­sion of re­ac­tion ar­rows (\rightleft­har­poons) with the pos­si­bil­ity to put text above and be­low. Anal­o­gous to ams­math's \xrightar­row and \xlef­t­ar­row this pack­age pro­vides the macro \xrightleft­har­poons. The pack­age re­quires ams­math. To use it, \usep­a­ck­age{chemarr}, then \xrightleft­har­poons[be­low]{above} .
The pack­age is part of the oberdiek bun­dle.